The present invention is related to processes for making strong, soft, absorbent fibrous webs, such as, for example, paper webs. More particularly, this invention is concerned with structured fibrous webs, equipment used to make such structured fibrous webs, and processes therefor.
Products made from a fibrous web are used for a variety of purposes. For example, paper towels, facial tissues, toilet tissues, napkins, and the like are in constant use in modern industrialized societies. The large demand for such paper products has created a demand for improved versions of the products. If the paper products such as paper towels, facial tissues, napkins, toilet tissues, mop heads, and the like are to perform their intended tasks and to find wide acceptance, they must possess certain physical characteristics.
Among the more important of these characteristics are strength, softness, and absorbency. Strength is the ability of a paper web to retain its physical integrity during use. Softness is the pleasing tactile sensation consumers perceive when they use the paper for its intended purposes. Absorbency is the characteristic of the paper that allows the paper to take up and retain fluids, particularly water and aqueous solutions and suspensions. Important not only is the absolute quantity of fluid a given amount of paper will hold, but also the rate at which the paper will absorb the fluid.
Through-air drying papermaking belts comprising a reinforcing element and a resinous framework, and/or fibrous webs made using these belts are known and described, for example, in the following commonly assigned U.S. Patent, the disclosures of which are incorporated herein by reference: U.S. Pat. No. 4,514,345, issued Apr. 30, 1985 to Johnson et al.; U.S. Pat. No. 4,528,239, issued Jul. 9, 1985 to Trokhan; U.S. Pat. No. 4,529,480 issued Jul. 16, 1985 to Trokhan; U.S. Pat. No. 4,637,859 issued Jan. 20, 1987 to Trokhan; U.S. Pat. No. 5,098,522, issued Mar. 24, 1992 to Smurkoski, et al.; U.S. Pat. No. 5,245,025 issued Sep. 14, 1993 to Trokhan et al.; U.S. Pat. No. 5,260,171, issued Nov. 9, 1993 to Smurkoski et al.; U.S. Pat. No. 5,275,700, issued Jan. 4, 1994 to Trokhan; U.S. Pat. No. 5,328,565, issued Jul. 12, 1994 to Rasch et al.; U.S. Pat. No. 5,334,289, issued Aug. 2, 1994 to Trokhan et al.; U.S. Pat. No. 5,431,786, issued Jul. 11, 1995 to Rasch et al.; U.S. Pat. No. 5,496,624, issued Mar. 5, 1996 to Stelljes, Jr. et al.; U.S. Pat. No. 5,500,277, issued Mar. 19, 1996 to Trokhan et al.; U.S. Pat. No. 5,514,523, issued May 7, 1996 to Trokhan et al.; U.S. Pat. No. 5,527,428 issued Jun. 18, 1996 to Trokhan et al.; U.S. Pat. No. 5,554,467, issued Sep. 10, 1996, to Trokhan et al.; U.S. Pat. No. 5,566,724, issued Oct. 22, 1996 to Trokhan et al.; U.S. Pat. No. 5,624,790, issued Apr. 29, 1997 to Trokhan et al.; U.S. Pat. No. 5,628,876 issued May 13, 1997 to Ayers et al.; U.S. Pat. No. 5,679,222 issued Oct. 21, 1997 to Rasch et al.; U.S. Pat. No. 5,714,041 issued Feb. 3, 1998 to Ayers et al.; U.S. Pat. No. 5,900,122 issued May 4, 1999 to Huston; and U.S. Pat. No. 5,948,210 issued Sep. 7, 1999 to Huston.
In the aforementioned belts of prior art the resinous framework is joined to the fluid-permeable reinforcing element (such as, for example, a woven structure, or a felt). The resinous framework may be continuous, semi-continuous, comprise a plurality of discrete protuberances, or any combination thereof. The resinous framework extends outwardly from the reinforcing element to form a web-side of the belt (i. e., the surface upon which the web is disposed during a papermaking process), a backside opposite to the web-side, and deflection conduits extending therebetween. The deflection conduits provide spaces into which papermaking fibers deflect under application of a pressure differential during a papermaking process. Because of this quality, such papermaking belts are also known in the art as xe2x80x9cdeflection members.xe2x80x9d The terms xe2x80x9cpapermaking beltxe2x80x9d and xe2x80x9cdeflection memberxe2x80x9d may be used herein interchangeably.
Papers produced on such deflection members, disclosed in the aforementioned patents, are generally characterized by having at least two physically distinct regions: a region having a first elevation and typically having a relatively high density, and a region extending from the first region to a second elevation and typically having a relatively low density. The first region is typically formed from the fibers that have not been deflected into the deflection conduits, and the second region is typically formed from the fibers deflected into the deflection conduits of the deflection member. The papers made using the belts having a continuous resinous framework and a plurality of discrete deflection conduits dispersed therethrough comprise a continuous high-density network region and a plurality of discrete low-density pillows (or domes), dispersed throughout, separated by, and extending from the network region. The continuous high-density network region is designed primarily to provide strength, while the plurality of the low-density pillows is designed primarily to provide softness and absorbency. Such belts have been used to produce commercially successful products, such as, for example, Bounty(copyright) paper towels, Charmin(copyright) toilet tissue, and Charmin Ultra(copyright) toilet tissue, all produced and sold by the instant assignee.
Typically, certain aspects of absorbency of a fibrous structure are highly dependent on its surface area. That is, for a given fibrous web (including a fiber composition, basis weight, etc.), the greater the web""s surface area the higher the web""s absorbency. In the structured webs, the low-density pillows, dispersed throughout the web, increase the web""s surface area, thereby increasing the web""s absorbency. However, increasing the web""s surface area by increasing the area comprising the relatively low-density pillows would result in decreasing the web""s area comprising the relatively high-density network area that imparts the strength. That is, increasing a ratio of the area comprising pillows relative to the area comprising the network would negatively affect the strength of the paper, because the pillows have a relatively low intrinsic strength compared to the network regions. Therefore, it would be highly desirable to minimize the trade-off between the surface area of the high-density network region primarily providing strength, and the surface area of the low-density region primarily providing softness and absorbency.
Now, it has been discovered that the areas of the high-density region and the low-density region can be effectively de-coupled in a fibrous structure, e. g., that the surface area of the fibrous structure may be increased without sacrificing the strength of the fibrous structure. Specifically, it has been discovered that the surface area of the relatively low-density and absorbent pillows can be sufficiently increased, without decreasing the area of the relatively high-density network, by forming a novel fibrous structure using a deflection member of the present invention.
Accordingly, the present invention provides a novel strong, soft, and absorbent fibrous structure and a process for making such a fibrous structure. More specifically, the present invention provides a fibrous structure that has at least two regions: a first region having a first elevation and a second region extending from the first region to define a second elevation, the second region having an increased surface area that enhances absorption qualities of the fibrous structure.
The present invention further provides a fibrous structure wherein the second region comprises fibrous domes and fibrous cantilever portions laterally extending from the domes. The fibrous cantilever portions increase the surface area of the second region and form, in some embodiments, pockets comprising substantially void spaces between the fibrous cantilever portions and the first region. These pockets are capable of receiving additional amounts of liquid and thus further increase absorbency of the fibrous structure.
The present invention also provides novel deflection members useful for making such structured fibrous structures. More specifically, the present invention provides deflection members comprising a patterned framework having suspended portions that form voids into which the fibers can be deflected during a process for making the fibrous structure of the present invention, to form the fibrous cantilever portions.
The present invention further provides processes for making such deflection members. In one embodiment, such a deflection member comprises a multi-layer framework formed by at least two layers joined together in a face-to-face relationship. Each of the layers has a deflection conduit portion. The deflection conduit portion of one layer is fluid-permeable and positioned such that portions of that layer correspond to the deflection conduits of the other layer and thus comprise a plurality of suspended portions.
In another embodiment, such a deflection member comprises a single-layer framework wherein the suspended portions are formed by curing a layer of a curable material through a novel mask of the present invention, comprising regions of differential opacities.
In still another embodiment, the deflection member can be made by curing a coating of the curable material through a novel mask of the present invention, comprising opaque regions and transparent regions, and a three-dimensional topography.
The present invention further provides novel masks that can be used in a process for selective curing of a curable material, such as, for example, a photosensitive resinous material. Such masks can also be used in making deflection members of the present invention. More specifically, the present invention provides a mask having a pattern of transparent regions and opaque regions, the opaque regions comprising differential opacity.
The present invention also provides a mask in which the opaque regions comprise a gradient opacity that gradually changes in at least one direction. The present invention further provides a mask having a combined pattern comprising a pattern of the transparent/opaque regions and a three-dimensional pattern of protrusions extending from at least one side of the mask. The present invention also provides processes for making the masks of the present invention.
A deflection member of the present invention comprises a framework having a web-side and a backside opposite to the web-side. The framework can be made of any suitable material, including, without limitation, a resinous material (such as, for example, a photosensitive resin), a plastic, a metal, metal-impregnated polymers, etc. The back side of the framework defines an X-Y plane. A thickness of the framework extends between the web-side and the backside in a Z-direction perpendicular to the X-Y plane.
The framework comprises a plurality of bases extending from the X-Y plane in the Z-direction, and a plurality of suspended portions laterally extending from the plurality of bases, wherein the suspended portions are elevated in the Z-direction from the X-Y plane to form void spaces between the X-Y plane and the suspended portions. While the suspended portions themselves do not need to be parallel to the X-Y plane, it is said that the suspended portions can xe2x80x9cextendxe2x80x9d in directions substantially parallel to the X-Y plane, to indicate that the suspended portions extend xe2x80x9claterallyxe2x80x9d from the bases (i. e. not parallel to the Z-direction).
In one embodiment, the framework comprises a multi-layer (laminated) structure formed by at least two layers: a first layer and a second layer joined together in a face-to-face relationship. Each of the layers has a top surface and a bottom surface opposite to the top surface. Each of the layers can have a conduit portion comprising at least one deflection conduit extending in the Z-direction from the top surface toward the bottom surface. The conduit portion can extend from the top surface to the bottom surface through the entire thickness of the layer. The bottom surface of the first layer forms the backside of the framework, and the top surface of the second layer forms the web-side of the framework. In a multi-layer embodiment of the deflection member (i. e., the deflection member comprising a plurality of layers), the plurality of bases is formed by the first layer.
According to the present invention, in an exemplary dual-layer deflection member (i. e., the deflection member comprising two layers), the second layer comprises a plurality of suspended portions elevated in the Z-direction from the X-Y plane to form void spaces between the X-Y plane and the suspended portions. During a process of making a fibrous structure of the present invention, these void spaces can receive a plurality of fibers to form fibrous cantilever portions of the fibrous structure being formed.
The deflection member of the present invention can further comprise a reinforcing element positioned between the web-side and at least a portion of the backside of the framework. The reinforcing element can be fluid-permeable, fluid-impermeable, or partially fluid-permeable (meaning that some portions of the reinforcing element may be fluid-permeable, while other portions thereof may be not). Examples of the reinforcing element include, without limitation, a woven element, a felt, a mesh wire, or a combination thereof. In the embodiment comprising the multi-layer deflection member, the reinforcing element is typically positioned between the top surface of the first layer and at least a portion of the bottom surface of the first layer, in which instance, the void spaces are formed between the reinforcing element and the suspended portions of the second layer.
In a multi-layer deflection member of the present invention, each of the layers can comprise a substantially continuous framework, a substantially semi-continuous framework, a plurality of discrete protuberances, or any combination thereof. In the exemplary dual-layer deflection member, examples of combinations of the first and second layers include, without limitation, the following: the deflection member, wherein the first layer comprises a substantially continuous patterned network defining a first plurality of discrete deflection conduits therewithin, and the second layer comprises a substantially continuous patterned network defining a second plurality of discrete deflection conduits therewithin; the deflection member, wherein the first layer comprises a substantially continuous patterned network defining a first plurality of discrete deflection conduits therewithin, and the second layer comprises a semi-continuous patterned network; the deflection member, wherein the first layer comprises a substantially continuous patterned network defining a first plurality of discrete deflection conduits therewithin, and the second layer comprises a plurality of discrete protuberances; the deflection member, wherein the first layer comprises a semi-continuous patterned network, and the second layer comprises a substantially continuous patterned network defining a second plurality of discrete deflection conduits therewithin; the deflection member, wherein the first layer comprises a first semi-continuous patterned network, and the second layer comprises a second semi-continuous patterned network; the deflection member, wherein the first layer comprises a semi-continuous patterned network, and the second layer comprises a plurality of discrete protuberances; the deflection member, wherein the first layer comprises a plurality of discrete protuberances, and the second layer comprises a substantially continuous patterned network defining a second plurality of discrete deflection conduits therewithin; the deflection member, wherein the first layer comprises a plurality of discrete protuberances, and the second layer comprises a semi-continuous patterned network; the deflection member, wherein the first layer comprises a first plurality of discrete protuberances, and the second layer comprises a second plurality of discrete protuberances.
The first layer and/or the second layer may be fluid-impermeable or partially fluid-permeable. One example of the partially-fluid permeable layer comprises a layer having a plurality of deflection conduits, wherein at least some of the deflection conduits are xe2x80x9cclosedxe2x80x9d with a fluid-impermeable material.
A process for making the multi-layer deflection member comprises the following steps:
forming a first layer having a top surface and a bottom surface opposite to the top surface and defining an X-Y plane, the first layer further having a first conduit portion extending between the top and bottom surfaces of the first layer;
forming a second layer having a top surface, a bottom surface opposite to the top surface, and a second conduit portion extending between the top and bottom surfaces of the second layer; and
joining the first layer and the second layer together in a face-to-face relationship such that the top surface of the first layer faces the bottom surface of the second layer, wherein suspended portions of the second layer corresponding to the first conduit portion of the first layer are spaced at a distance from the X-Y plane to form void spaces between the X-Y plane and the suspended portions of the second layer.
Either one or both of the first layer and the second layer may be formed by a process comprising the following steps:
providing a coating of a liquid photosensitive resin supported by a forming surface, the coating having a first thickness;
providing a source of curing radiation;
providing a mask having a pre-selected pattern of transparent regions and opaque regions therein and positioning the mask between the coating of the liquid photosensitive resin and the source of curing radiation so that the opaque regions of the mask shield areas of the coating from the curing radiation while the transparent regions of the mask cause other areas of the coating to be unshielded;
curing the unshielded areas of the coating by exposing the coating to the curing radiation through the mask while leaving the shielded areas of the coating uncured, thereby forming a partly-formed layer;
removing substantially all uncured liquid photosensitive resin from the partly-formed layer to leave a hardened resinous structure.
Optionally, a backing film may be provided and positioned between the forming surface and the coating of a liquid photosensitive resin, to protect the forming surface from being contaminated by the liquid resin.
Alternatively or additionally to the process of making the layers described herein above, each or both of the layers can be formed by providing a ply of a predetermined thickness and forming therein a plurality of apertures of predetermined shapes and according to a pre-selected pattern.
If the deflection member having the reinforcing element is desired, the process may further include steps of providing a suitable reinforcing element supported by the forming surface, the reinforcing element having a lower side facing the forming surface and an upper side opposite to the lower side, and depositing the coating of a liquid photosensitive resin to the upper side of the reinforcing element.
Optionally, a thickness of the coating can be controlled by, for example, a roll, a bar, a knife, or any other suitable means known in the art.
In one embodiment, the first and second layers are produced simultaneously on two respective forming surfaces and then are joined together, upon contact, in a press nip. According to one embodiment of the present invention, a step of maintaining at least one of the top surface of the first layer and the bottom surface of the second layer in a partially uncured condition is required to enable the first and second layers to join together upon contact therebetween. Alternatively or additionally, the first and second layers can be joined by using an adhesive material. In one embodiment, the top surface of the first layer and/or the bottom surface of the second layer comprise(s) a chemically-active ingredients causing or facilitating joining together of the first and second layers.
Each of the suspended portions has a web-oriented surface comprising the web-side of the framework, and a back surface opposite thereto. The void spaces formed between the suspended portions and the X-Y plane, or between the suspended portions and the reinforcing element, are formedxe2x80x94more specificallyxe2x80x94between the back surfaces of the suspended portions and either the X-Y plane or the reinforcing element. A plurality of shapes and configurations of the back surfaces of the suspended portions are contemplated in the present invention, all of which could be formed using one of the processes of the present invention. The suspended portion may have the back surface that is substantially parallel to the X-Y plane. The suspended portion may also have the back surface that is not parallel to the web-oriented surface. The suspended portion may have curving, circular, xe2x80x9cwavingxe2x80x9d back surfaces, or back surfaces having different irregular shapes.
When viewed in a particular cross-section perpendicular to the X-Y plane, the suspended portion may form either a xe2x80x9ccantileverxe2x80x9d portion or a xe2x80x9cbridgexe2x80x9d portion in a cross-section. As used herein, the xe2x80x9ccantileverxe2x80x9d suspended portion means the suspended portion that has at least one free end in a cross-section perpendicular to the X-Y plane, while the xe2x80x9cbridgingxe2x80x9d suspended portion is the suspended portion that interconnects (or xe2x80x9cbridgesxe2x80x9d) at least two bases in a cross-section perpendicular to the X-Y plane.
Analogously with the differential patterns of the layers, described above, the web-side and the backside of the framework may comprise a substantially continuous pattern, a substantially semi-continuous pattern, or a pattern formed by a plurality of discrete protuberances. The difference between the patterns as regards the framework as a whole and the patterns as regards the web-side or backside surfaces of the framework is that in the context of the framework as a whole, the entire thickness of the framework is under consideration for the purposes of continuity, semi-continuity, or discontinuity of the framework; while in the context of the web-side and the backside of the framework, only a relevant surface (of the web-side or the backside) is under consideration for the purposes of continuity, semi-continuity, or discontinuity of that relevant surface.
The framework as a whole, whether multi-layer or single-layer, may have a fluid-permeable conduit portion extending from the web-side to the backside of the framework. In one embodiment, at least one of the web-side and the backside of the framework comprises a substantially continuous pattern of a plurality of discrete openings dispersed therethrough, wherein the plurality of discrete openings comprises a plurality of discrete deflection conduits. Some of the plurality of openings in the web-side or the backside may be closed by a fluid-impermeable material to form fluid-impermeable portions of the framework, if desired.
Another embodiment of a process for making a deflection member, or a single layer thereof, comprises the following steps:
providing a coating of a liquid photosensitive resin supported by a forming surface, the coating having a top surface, a bottom surface opposite thereto and facing the forming surface, and a pre-selected first thickness defined between the top and bottom surfaces;
providing a source of curing radiation;
providing a mask having transparent regions and opaque regions, the opaque regions comprising at least first opaque regions and second opaque regions, the first opaque regions having a first opacity, and the second opaque regions having a second opacity less that the first opacity;
positioning the mask between the coating and the source of curing radiation;
curing the liquid photosensitive resin through the mask, wherein the first opaque regions shield first areas of the coating from the curing radiation to preclude curing of the first areas of the coating through the first thickness of the coating, the second opaque regions partially shield second areas of the coating to allow the curing radiation to cure the second area of the coating to a predetermined second thickness less than the first thickness of the coating, and the transparent regions leave third areas of the coating unshielded to allow the curing radiation to cure the third areas through the first thickness of the coating, thereby forming a partly-formed deflection member; and
removing substantially all uncured liquid photosensitive resin from the partly-formed deflection member to leave a hardened resinous structure which forms a macroscopically monoplanar, patterned framework having a web-side formed from the top surface of the coating, and a backside formed from the bottom surface of the coating and defining an X-Y plane.
The resulting framework comprises a plurality of bases formed from the third areas of the coating and a plurality of suspended portions formed from the second areas of the coating, wherein the suspended portions laterally extend from the plurality of bases and are spaced from the X-Y plane to form void spaces between the X-Y plane and the suspended portions.
A fibrous structure of the present invention comprises at least two regions: a first plurality of micro-regions (or simply a first region) defining a first plane and having a first elevation, and a second plurality of micro-regions (or simply a second region) outwardly extending from the first plane to define a second elevation, wherein at least some of the second plurality of micro-regions comprise a fibrous dome and a fibrous cantilever portion extending laterally from the dome at a second elevation. As used herein, the fibrous dome and the cantilever portion extending therefrom comprise a xe2x80x9cpillow.xe2x80x9d It is to be understood, however, that some pillows may not have the cantilever portion.
Each of the first and second pluralities of micro-regions can be substantially continuous, substantially semi-continuous, be formed by a plurality of discrete protuberances, or comprise a combination thereof. If the first plurality of micro-regions comprises a substantially continuous and macroscopically monoplanar network area, the second plurality of micro-regions can comprise a plurality of discrete pillows dispersed throughout the network area, at least some of the pillows comprising the fibrous dome extending from the network area and the fibrous cantilever portion laterally extending from the dome.
Some of the fibrous cantilever portions are elevated from the first plane to form pockets comprising substantially void spaces between the first plane and the fibrous cantilever portion. These pockets are believed to provide additional room for receiving liquids during the use of the fibrous structure and thus enhance its absorptive properties. The fibrous cantilever portions of the fibrous structure also increase its overall surface area, thereby further contributing to increasing the absorptive properties of the fibrous structure. In a cross-section perpendicular to the X-Y plane, a ratio of an overall cross-sectional perimeter of at least one of the pillows comprising the fibrous cantilever portion to a cross-sectional base of said pillow is 4/1 or greater.
Some of the pillows, whether they comprise a continuous pattern, a semi-continuous pattern, or a pattern of discrete protuberances, may not have a well-defined fibrous cantilever portion in a cross-section perpendicular to the X-Y plane. But even without the fibrous cantilever portions, the fibrous structure of the present invention provides the benefit of an increased surface area of the second plurality of micro-regions. Therefore, in another aspect, the fibrous structure of the present invention comprises a first plurality of micro-regions defining a first plane and having a first elevation and a second plurality of micro-regions outwardly extending from the first plane to form a second elevation, wherein in at least one cross-section perpendicular to the first plane the second plurality of micro-regions comprises a pillow having a cross-sectional perimeter and a cross-sectional base measured at the first elevation, wherein a ratio of the cross-sectional perimeter to the cross-sectional base is 4/1 or greater.
The differential regions of the fibrous structure may have differential basis weights and/or differential densities, and/or differential fiber compositions. In one embodiment, a density of the first plurality of micro-regions is greater than a density of the second plurality of micro-regions. In another embodiment, a basis weight of the second plurality of micro-regions is greater than a basis weight of the first plurality of micro-regions. In still another embodiment, a ratio of the amount of long fibers relative to the amount of short fibers can be varied such that that ratio is 1.0, greater than 1.0, or less than 1.0. The fibrous structure of the present invention can have an intermediate density relative to the high density of the first plurality of micro-regions and the low density of the second plurality of micro-regions. The fibrous cantilever portions may have such an intermediate density.
A laminated structure of the present invention comprises at least two laminae. A least one of the laminae comprises the fibrous structure described above. In one embodiment, the laminated fibrous structure of the present invention comprises at least a first lamina and a second lamina joined together. The first lamina comprises a fibrous sheet having at least two regions and comprising a first plurality of micro-regions defining a first plane and having a first elevation, and a second plurality of micro-regions comprising a plurality of fibrous domes outwardly extending from the first plane to define a second elevation and a plurality of fibrous cantilever portions laterally extending from the domes at the second elevation. The other lamina or laminae in the laminated structure may or may not have fibrous cantilever portions. Of course, the other lamina or laminae may be made by any process known in the art, including, without limitation, through-air-drying and conventional processes. The laminae can be joined such that the fibrous cantilever portions of one lamina face the other lamina. Alternatively, the laminae having the fibrous cantilever portions can be joined by a side opposite to that having the fibrous cantilever portions.
In the laminated fibrous structure comprising at least two laminae, each laminae can have the fibrous cantilever portions spaced from the first plane to form pockets comprising substantially void spaces between the first plane and the fibrous cantilever portions. Then, if the two laminae are joined together such that the fibrous cantilever portions of one lamina face the fibrous cantilever portions of the other lamina, at least some of the fibrous cantilever portions of one lamina can be disposed in the pockets formed between the fibrous cantilever portions and the first plane of the other lamina. Such a joining of two laminae is believed to provide a limited movability of the laminae relative to one another in at least one lateral direction, without tearing of either lamina or separation of the laminae. Such a movability is believed to facilitate softness and absorbency of the laminated fibrous structure of the present invention. Alternatively, the laminae can be joined such that their respective fibrous cantilever portions face opposite directions.
A process for making a fibrous structure of the present invention comprises the following steps:
providing the deflection member of the present invention, described above;
providing a plurality of fibers and depositing the plurality of fibers on the deflection member;
deflecting a portion of the plurality of fibers into the deflection conduits of the deflection member such as to cause some of the deflected fibers or portions thereof to be disposed within the void spaces formed between the X-Y plane and the suspended portions of the deflection member, thereby forming a partly-formed fibrous structure; and
separating the partly-formed fibrous structure from the deflection member, thereby forming the fibrous structure of the present invention.
The process can further comprise a step of pressing the deflection member having the partly-formed fibrous structure thereon against a pressing surface, such as, for example, a surface of a Yankee drying drum, thereby densifying portions of the partly-formed fibrous structure.
The step of deflecting a portion of the plurality of fibers may comprise applying a mechanical pressure to the portion of the fibers, or a fluid pressure differential, such as, for example, a vacuum pressure, to the plurality of fibers. In one embodiment, a web disposed on the deflection member can be overlaid with a flexible sheet of material such that the web is disposed between the flexible sheet of material and the deflection member. The flexible sheet of material has an air permeability less than that of the deflection member. The flexible sheet of material can also be air-impermeable. An application of a fluid pressure differential to the sheet of material causes deflection of at least a portion of the sheet of material towards the papermaking belt and deflection of at least a portion of the web into the conduits of the papermaking belt.
The plurality of fibers can be selected from any fibers known in the art, for example, cellulosic fibers, synthetic fibers, or any combination thereof. The plurality of fibers can also be supplied in the form of a moistened fibrous web in which portions of the web could be effectively deflected into the deflection conduits and the void spaces formed between the suspended portions and the X-Y plane of the deflection member.
The present invention also provides a mask for use in a process for curing a curable material, such as, for example, a photosensitive resinous material, suitable for making the deflection member of the present invention. In one embodiment, the mask of the present invention comprises a structure having a top side and a bottom side opposite to the top side, and a pattern of transparent regions and opaque regions, wherein the opaque regions comprise at least first opaque regions having a first opacity and second opaque regions having a second opacity different from the first opacity.
The transparent regions and the opaque regions can comprise a non-random and repeating pattern. The opaque regions can comprise a substantially continuous pattern, a substantially semi-continuous pattern, a pattern formed by a plurality of discrete areas, or any combination thereof. Furthermore, the first opaque regions and the second opaque regions can comprise a non-random and repeating pattern. The first opaque regions, the second opaque regions, or both of the first and second opaque regions can comprise a substantially continuous pattern, a substantially semi-continuous pattern, a pattern formed by a plurality of discrete areas, or any combination thereof. The second opaque regions can be adjacent to or separated from the first opaque regions.
The opaque regions can comprise more than two differential opacities. For example, the mask according to the present invention can comprise third opaque regions having a third opacity intermediate the first opacity and the second opacity.
In one embodiment, the opaque regions comprise a gradient opacity that gradually changes in at least one direction. The region of gradient opacity may comprise the first opaque region, the second opaque region, or be separate from those. The gradient opacity can change, in equal increments or alternatively in unequal increments, in one or several directions.
In another embodiment, the mask comprises a three-dimensional topography, such as, for example, a pattern of protrusions extending from at least one side of the mask. Protrusions extending from the bottom side of the mask can be structured and configured to be imprinted into the coating of a curable material to form corresponding depressions, or voids, in the coating. Protrusions extending from the top side of the mask can be structured and configured to provide voids into which the liquid curable material can flow to approximate the contours of the mask""s topography. Either one or both of the patterns of protrusions can comprise a substantially continuous pattern, a substantially semi-continuous pattern, a pattern formed by a plurality of discrete protuberances, or any combination thereof. Either one or both of the patterns of protrusions can correlate with the pattern of transparent regions and opaque regions to form a combined non-random and repeating pattern. In one such embodiment, the opaque regions comprise distal surfaces of the protrusions.
In one embodiment of the mask, the pattern of transparent and opaque regions is independent and separable from the pattern of the protrusions. Such a mask can comprise a composite structure formed by at least a first element and a second element juxtaposed therewith in a face-to-face relationship, wherein the first element forms the pattern of transparent and opaque regions, and the second element forms the pattern of protrusions. The first and second elements in such a composite mask can be superimposed to form a combined non-random and repeating pattern of the opaque regions and the protrusions.
The mask having differential opacities can be used in a process for curing a curable material for constructing the deflection member of the present invention. For example, when the mask comprising the first and second opacities is positioned between the source of curing radiation and a coating of the curable material, to selectively shield the coating from the curing radiation, the first opaque regions having a first opacity shield first areas of the coating from the curing radiation to cause the first regions to remain uncured through the entire thickness of the coating, the second opaque regions having the second opacity partially shield second areas of the coating to allow the curing radiation to cure the coating through a partial thickness less than the entire thickness of the coating, and the transparent regions leave third areas of the coating unshielded to allow the curing radiation to cure the curable material through its entire thickness.
If the mask having gradient opacity is used for curing a coating, a region having the gradient opacity shields a corresponding area of the coating from the curing radiation such as to cause said corresponding area to cure through a gradually changing thickness correlating with the gradually changing opacity of the mask""s gradually-opaque region. For example, if the gradient opacity changes (increases or decreases) in equal increments or decrements in one direction, a depth of curing of the corresponding area of the coating will also change gradually in equal decrements or increments. Of course, the gradient opacity may change in unequal increments.
The mask of the present invention can be made by a process comprising the steps of providing a thin transparent material of substantially uniform thickness, such as, for example, a transparent film; forming a pattern of opaque regions on the material according to a first predetermined pattern; and embossing the material according to a second predetermined pattern. The process can be structured such that the first predetermined pattern substantially correlates with the second predetermined pattern to form a combined non-random repeating pattern. For example, the steps of forming the opaque regions and embossing the material can be performed simultaneously. The step of forming a pattern of opaque regions can comprise applying ink to selected regions of the thin transparent material. The selected regions can comprise distal surfaces of the embossed areas of the material.
The mask having regions of differential opacities can be formed in a multi-step process comprising printing a transparent film to form a pattern of opaque regions having a certain initial opacity, and then printing the film a second (third, fourth, etc.) time, as needed, to form a pattern (or patterns) of opaque regions having another opacity (or other opacities), different from the initial opacity (or different from one another). The differential opacities can also be formed in one-step printing, for example, by a Gravure roll comprising a pattern having a differential depths for receiving ink. During printing, the ink transferred from the Gravure roll to the transparent film will have regions of differential intensities, reflecting the differential depths of the roll""s pattern. Other methods of forming opaque regions can be used in the present invention, including, without limitation, chemical, electromagnetic, laser, heat, etc.
In another aspect, a process for making the deflection member of the present invention, using a three-dimensional mask described above, comprises the following steps:
providing a coating of a liquid curable material supported by a forming surface, the coating having a bottom surface facing the forming surface, a top surface opposite to the bottom surface, and a first thickness defined between the top and bottom surfaces;
providing a source of curing radiation structured and configured to emit a curing radiation to cure the coating supported by the forming surface;
providing a mask having a first pattern of transparent regions and opaque regions therein, and a second pattern of protrusions outwardly extending from one side of the mask;
positioning the mask between the coating and the source of curing radiation such that the second pattern of protrusions is at least partially submerged into the coating, thereby forming three-dimensional voids therein;
curing the curable material, wherein the opaque regions of the first pattern at least partially shield selected areas of the coating from the curing radiation such that the selected areas are cured through at least a portion of the first thickness, thereby forming a partly-formed deflection member; and
removing substantially all uncured material from the partly-formed deflection member to leave a hardened resinous structure which forms the deflection member comprising a macroscopically monoplanar, patterned framework having a web-side formed from the top surface of the coating, and a backside formed from the bottom surface of the coating.
As explained above, the first pattern, the second pattern, or both the first and second patterns can be non-random and repeating. Depending on a specific embodiment of the mask, the mask can be positioned such that the second pattern of protrusions is submerged into the selected areas that are at least partially shielded by the opaque regions of the first pattern of the mask. Alternatively or additionally, the mask can be positioned such that that the second pattern of protrusions is submerged into the areas that are not shielded by the opaque regions of the first pattern of the mask.
In one embodiment, the mask comprises a composite structure formed by at least a film and an embossing element juxtaposed therewith, the embossing element forming the second pattern of protrusions. In such an embodiment, the embossing element, the film, or both the embossing element and the film can comprise opaque regions. If both the embossing element and the film comprise opaque regions, it may be beneficial to provide that the opaque regions of the embossing element and the opaque regions of the film are mutually coordinated to form the first pattern of transparent and opaque regions.
The embossing element can be transparent to the curing radiation. Alternatively, the embossing element can be impermeable to the curing radiation. In one embodiment, the embossing element has voids therethrough. Such an embossing element can comprise, for example, and without limitation, a woven element having open areas therethrough, or a mesh wire.
A process for making a deflection member, using the composite mask can comprise the following steps:
providing a coating of a liquid curable material supported by a forming surface, the coating having a bottom surface facing the forming surface, a top surface opposite to the bottom surface, and a first thickness defined between the top and bottom surfaces;
providing a source of curing radiation structured and configured to emit a curing radiation to cure the coating of the liquid curable material supported by the forming surface;
providing an embossing element and juxtaposing the embossing element with the top surface of the coating such that the embossing element is at least partially submerged into the coating, thereby forming a pattern of voids in the coating;
providing a film and juxtaposing the film with the embossing element, wherein the embossing element and the film in combination comprise a pattern of transparent regions and opaque regions, wherein the opaque regions shield areas of the coating from the curing radiation, while the transparent regions cause other areas of the coating to be unshielded;
curing the unshielded areas of the coating by exposing the coating to the curing radiation through the embossing element and the film, while leaving the shielded areas of the coating uncured, thereby forming a partly-formed deflection member; and
removing substantially all uncured material from the partly-formed deflection member to leave a hardened resinous structure comprising a macroscopically monoplanar, patterned framework having a web-side formed from the top surface of the coating, and a backside formed from the bottom surface of the coating.
In its industrial application, each of the processes of making the deflection member, described herein, can comprise a continuous process. For example, the continuous process of making the deflection member, using the three-dimensional mask, comprises the following steps:
providing a coating of a liquid curable material supported by a forming surface, and continuously moving the forming surface with the coating in a machine direction, the coating having a bottom surface facing the forming surface, a top surface opposite to the bottom surface, and a first thickness defined between the top and bottom surfaces;
providing a source of curing radiation structured and configured to emit a curing radiation to continuously cure the coating supported by the forming surface moving in the machine direction;
continuously providing a transparent film; continuously printing the film to form a first pattern of opaque regions therein; continuously embossing the film to form a second pattern of protrusions therein; continuously moving the film having the first pattern of opaque regions and the second pattern of protrusions to position said film between the coating and the source of curing radiation such that the second pattern of protrusions is at least partially submerged into the coating, thereby forming three-dimensional voids therein;
continuously curing the curable material, wherein the opaque regions of the first pattern at least partially shield selected areas of the curable material from the curing radiation such that the selected areas are cured through at least a portion of the first thickness of the coating, thereby forming a partly-formed deflection member; and
continuously removing substantially all uncured material from the partly-formed deflection member to leave a hardened resinous structure comprising a macroscopically monoplanar, patterned framework having a web-side formed from the top surface of the coating, and a backside formed from the bottom surface of the coating.